Modern society relies on the functionality of mobile devices more and more as the development of the telecommunication technology and the changed habit of the people to hold together their relationship. To draw consumers' attention, other than the common communication functionality, various mobile devices in the market add more fancy ones, and the most popular one among them is the personal information storage functionality which may be implemented through the mass storage space provided by a internal memory and/or a removable memory card. Therefore, those personal information, such as phone books, pictures, text messages, music files, or other types of personal information could be all stored in this space.
However, as the mobile devices get lighter and smaller to become easy for carry, they are inevitably easy to get lost. If this happened, the stored personal information could be accessed or used by others. Thus, it is still needed to improve the information security of the personal information stored in the mobile devices.